1. Field of the Invention
This invention relates, generally, to a method for improving the visibility of a hyperechoic marker under ultrasound. Such markers are used to indicate the location of a tumor or lesion so that a procedure to remove such lesion or tumor may be performed weeks or months after the marker has been implanted. More particularly, it relates to markers that incorporate hydrogels to enhance the visibility of the markers with imaging techniques such as ultrasound and to methods for making such markers.
2. Description of the Prior Art
A permanent metal or hard plastic, such as a permanent, bio-compatible plastic such as polyethylene, or bioabsorbable, biocompatible plastic such as PGA/PLA, or other suitable marker must be left at a biopsy site at the completion of a biopsy if the site is to be located again in the future. Biodegradable markers are not permanent and therefore cannot be relied upon if a biopsy site is to be re-located at a time remote from the time of the biopsy. Suture and collagen-based markers are not suitable as markers because they are hyperechoic, i.e., difficult to see under ultrasound because such materials are easily confused with other shadowing normal structures in the body such as fibrous tissue, fatty tissue, ducts in breast tissue, and the like, for example. Such tissue provides a background clutter that masks the presence of a marker made of metal, hard plastic, or other hyperechoic material.
Water, unlike metal, hard plastic, and other hyperechoic materials, is hypoechoic, i.e., easy to see under imaging techniques such as ultrasound. Therefore it would be advantageous if a marker made of a hyperechoic material such as metal or hard plastic could be surrounded by an easily seen quantity of water.
However, the art includes no means for surrounding a hyperechoic marker with water at a biopsy site. There is a need, then, for a permanent marker that is surrounded by water after it has been positioned at a biopsy site.
A need also exists for a hydrogel manufacturing process that produces a cured and dehydrated plug or marker that contracts in length and increases in diameter upon being hydrated.
There is also a need for a hydrogel manufacturing process that produces a cured and dehydrated plug or marker that contracts in width and increases in length and height upon being hydrated.
There is also a further need for a hydrogel manufacturing process that produces a cured and dehydrated plug or marker that contracts radially and increases in length upon being hydrated.
However, in view of the prior art taken as a whole at the time the present invention was made, it was not obvious to those of ordinary skill how the identified needs could be fulfilled.